Although delivery devices are known for use in a vast variety of applications the present invention is mainly concerned with injection devices in applications where the injection receiving object is solid or semi-solid and wherein the orientation of the injection device relative the injection receiving object is critical to the proper outcome of the injection. Typical applications are the administration of pharmaceutical preparations to humans or animals where orientation is important for diverse reasons. Depending on the nature of the preparation and the intention of the treatment the target tissue is vital for correct biochemical activity, availability and absorbency period. The intended injection site may for example be subcutaneous, intramuscular or intravenous. The dose delivered is often critical and erroneous treatment may result both from lost preparation due to e.g. inadvertent needle release or partial placement in wrong tissue. Conversely, especially larger volumes may intentionally be distributed at several depth during needle penetration or partially in slow releasing tissue and partially in fast releasing tissue.
These demands can be met also when using the simplest injection devices, such as the common hypodermic syringe, when in the hands of a skilled operator who also may initiate medically relevant corrective measures in case of accidents and malfunction. More or less automated devices has since long existed to enable laymen with limited training performing injections with reasonable safety in critical or emergency situations. Often the devices are designed for single shots only. A general trend in long-term medication is to place the administration responsibility on the patient himself, also in the case of child or disabled persons. Here the demands are still higher. The continuous medication requires the patient to cope with repeated dosing, perhaps with varying dose setting and proper replacement of emptied cartridges with fresh ones as in pen-type injectors. A high degree of automation and control is desirable to avoid mistakes, not only at the mere injections steps but also the critical initiation and preparation steps. Patients dependent on daily administrations also have a legitimate need for convenience and devices discrete enough to be brought around in daily life.
Mechanical automation is provided in common autoinjectors. Typically the user is expected to position the device in proper injection orientation against the skin and operate a trigger button. Stored mechanical energy, e.g. in a spring system, may then perform autopenetration into the tissue, autoinjection of the medical and possibly also automatic needle retraction. Simpler systems may not provide autopenetration but assume the user to make the needle insertion. Hence the devices give the operator little assistance in orienting and localizing the devices in respect to the body. Autoinjectors are also known that require the operator to press the device against the injection site in order to trigger the injector. Typical examples are disclosed in AU 563.551, U.S. Pat. No. 4,717,384, EP 518.416 and WO 93/23110. The help provided by such constructions is limited and inflexible and cannot be adapted for different foreseeable operational or hazardous situations. Pressure rather than position based triggering makes desirable adaptations still more difficult. Generally, once triggering has occurred, either intentionally or inadvertently, the operation sequence proceeds irreversibly. Moreover, the dislocation risks are generally high in mechanical devices due to rebound effects and the forced transitions involved.
Automated devices based on electronic or electromechanical principles have also been proposed. Disregarding here infusion pumps and similar injection devices for primarily hospital or permanent use, where device orientation generally is not critical, several prior patent specifications, as represented by e.g. EP 143.895, EP 293.958, DE 2.710.433, WO 93/02720, WO 95/24233 and WO 97/14459 as well as our copending applications SE 9602610-9 (U.S. 60/021,397) and SE 9602611-7 (U.S. 60/021,293), relates to hand held devices for direct action against the body. The known devices take advantage of automation principles in several respects, such as the precise and reproducible injection possible with electric motors, motor assisted autopenetration and mixing or reconstitution, cartridge identification, sample analysis, injection data collection and manipulation, dose setting, injector orientation relative gravity for proper mixing or deaeration etc. In spite of this diversity the automated devices in this class do not deal with device orientation versus the injection receiving body and do not solve any problem relating thereto.
Accordingly there is a continuing need for injection devices assisting the user in device orientation related handling steps and preventing or ameliorate consequences of mistakes and misuse resulting therefrom, especially useful for patients under self-administration. Although the present invention has a more general utility, it will mainly be described against this background.